Links to Drive folder and page URLs containing hash marks will continue to work indefinitely, but this change could impact any Google Apps admins or employees who parse Drive folder or page URLs specifically for the “#” symbol or who use Chrome extensions that employ the old-style URLs for Drive navigation.

This change is currently live for Rapid release domains; the rollout to Scheduled release domains is planned for June 9th.

Release track:
Live on Rapid release, with Scheduled release to follow on June 9th